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Articles from 1998 In December


Sprayed Soybean Oil Lowers Odor, Gas Levels

Most of the emphasis on odor problems in hog operations focuses on manure storage systems.

Now there is evidence from a survey that more odor complaints were received during a year from building sources than from manure storage units.

Airborne dust particles are a major cause of poor quality environments in hog buildings. And those particles also carry toxic and odorous gases.

Removing dust can therefore improve air quality in confinement and reduce the amount of odors and gases being exhausted from these buildings into the atmosphere.

At the University of Minnesota, agricultural engineer Larry Jacobson developed a study for the '97/'98 winter to evaluate the odor and gas reduction potential of sprinkling soybean oil for dust control.

This study was performed at the West Central Experiment Station of the University of Minnesota in Morris. It was performed at two, side-by-side, off-site, modular nursery buildings.

Fill time was one week. The six-week trial ran from pigs weighing 15 lb. to about 50 lb. One barn was used for the oil treatment, the second as the control group. Although the soybean oil spraying began as soon as the first pigs were placed in the treatment barn, data collection didn't start until four to seven days after the spraying, or when the treatment rooms were filled to 180-head capacity.

Spraying was done with a handheld, commercial paint sprayer during morning chores. Spray was distributed as evenly as possible throughout the room, including pens and alleys. A "daily maintenance level" equal to about one cup of oil was applied to the treatment room each day. Before that, during the first four days that weaned pigs were added to the treatment barn, a somewhat heavier dose of the oil spray was applied.

Also, one day every two weeks a "surge" amount equal to the first spray application level replaced the maintenance level.

Since the trials were conducted during winter, only a variable-speed exhaust fan was run continuously to provide ventilation. Room temperatures began at 85 degrees F, were lowered 2 degrees for every week of the trial.

Weekly measurements were taken of odor, gas and dust levels in treatment and control barns.

Air was measured for odor with an olfactometer (by a trained odor panel). Hydrogen sulfide, ammonia and carbon dioxide were measured from the same air samples with either an electronic (Jerome) meter or colorimetric tubes. Dust concentrations were measured with gravimetric (weighing filters) methods. All samples were collected during a six-hour time span (10 a.m. to 4 p.m.).

There was an overall reduction in odor levels of the nursery pigs housed in the treated rooms. There was a consistently lower odor level as measured by the odor panel and expressed as odor units (o.u.).

In trial 1, average odor level of only 150 o.u. was recorded for the oil treatment and an average of 400 o.u. for the air in the rooms housing the control pigs.

Trial 2 revealed lower odor units in the air collected in the treatment room, compared to the control group, for the first three sampling times.

But that was not the case for the last two weeks. Odor units were fairly high during week 4 in the second trial and fairly low for the last week of collection.

According to Jacobson it is unknown why the odor levels changed so much during the last two weeks of trial 2 and why the oil treatment did not seem to be effective. He suggests there may have been some weather effect, since the winter trials coincided with a warming trend. See Figure 1 and Figure 2.

Hydrogen sulfide gas levels were reduced across the board as shown in Figure 3 and Figure 4. Average gas concentrations in the oil treatment rooms were 100 and 350 ppb for trials 1 and 2, respectively. Hydrogen sulfide levels in the control rooms were 250 ppb in trial 1 and 550 ppb in trial 2.

The oil treatment program had no impact upon ammonia levels. Treated rooms recorded 10 ppm, untreated 9 ppm in trial 1. Similar levels were seen in trial 2 as the treated room had concentrations of 11 ppm and 10 ppm in the control rooms.

Growth performance was also monitored during the trials. Results indicated that pigs in both the treatment and the control groups performed well. Average daily gain and feed efficiency were both lower in the treated group in the first trial, but during the second trial, performance was almost identical in the treatment and control groups. Mortality averaged 1% for both nursery barns in trial 1, 3% and 0% for the control and treatment rooms, respectively, in the second trial.

The first trial ran December 1997 to January 1998. The second trial ran February to March 1998.

Researcher: Larry Jacobson, University of Minnesota, St. Paul, MN. Phone: (612) 625-8288.

Conjugated Linoleic Acid Effects Studied

Purdue University animal scientists are investigating the difference between the effects of conjugated linoleic acid (CLA) and the effects of lower feed intake on pig growth and carcass composition in lean genotype pigs.

Conjugated linoleic acid refers to a group of linoleic acid isomers that seem to have several biological effects. Scientists at the first annual CLA Forum reported pigs fed CLA had less backfat, less carcass fat, more carcass lean, improved feed conversion and firmer carcasses. Feeding CLA seemed to result in decreased feed intake while growth rate was unchanged, thus improving feed efficiency. The few studies that have been done regarding CLA for swine diets are shown in Table 3. These studies have seemed to show that CLA decreases backfat and increases fat firmness, but have been inconclusive in determining the effects of CLA on growth traits.

The Purdue researchers randomly assigned 30 lean-genotype gilts to one of three dietary treatments, starting at 165 lb. live weight. The diets consisted of conventional corn-soybean meal diets, supplemented with either 1.0% CLA-60 ad libitum (this was called the CLA diet), 1.0% sunflower oil ad libitum (SFO) or 1.0% sunflower oil restricted to the feed intake level of the CLA-fed group (RSFO).

Feed intake of the CLA pigs was determined weekly and fit to a quadratic equation as a function of live weight. This equation was used to determine the daily feed intake for the RSFO pigs. The design of the trial allowed the researchers to differentiate between the effects of CLA and the effects of lower feed intake on changes in growth and carcass composition.

Individual live weights and feed intake were obtained weekly for seven weeks. Ultrasonic, 10th- rib backfat and loin eye area images were collected weekly. These images were used to model lean growth and individual backfat layer growth. Pigs were slaughtered, tissue was collected and carcasses were evaluated at the Purdue Meat Laboratory. At slaughter, outer, middle and inner layer backfat, belly fat and loin were collected and snap frozen in liquid nitrogen until assayed for lipid and fatty acid composition. Standard carcass measurements such as backfat depths, loin eye area and subjective loin eye quality (color, firmness/wetness and marbling) were taken at 24 hours postmortem. Standardized loin slices were obtained for drip loss and for chemical analysis of fat and CLA. Bellies were removed from the carcasses and subjectively graded for firmness.

CLA-fed pigs demonstrated lower average daily gain (ADG). CLA-fed pigs also tended to have lower average daily feed intake (ADFI) and to be less feed efficient (FE), although the researchers say the results were not significant for these traits (Table 4). Restricted sunflower oil-fed pigs performed poorly in terms of ADG, ADFI and FE, which suggests the effects of CLA on the growth of pigs may be due to the effect of CLA on feed intake.

Neither the CLA or RSFO treatments had an effect on dressing percentage, ultimate (24-hour) pH, loin eye area, or subjective evaluations of loin color, firmness or marbling. Analysis of percent intramuscular fat remains in progress and will be reported in the future.

Both the CLA and RSFO treatments demonstrated a tendency, although not statistically significant, to improve drip loss and decrease kidney fat. The CLA-fed pigs tended to have less backfat, while the RSFO pigs tended to have more (Table 4). Although these differences in backfat were not significant, they demonstrate the effects of CLA on backfat thickness are not simply due to changes in feed intake.

CLA dramatically increased the firmness of bellies. RSFO treatment had a detrimental effect on belly firmness (Table 4). Approximately 50% of the SFO bellies for this genotype of pigs were questionable in terms of being firm enough to slice, while even the thinnest CLA-fed bellies were acceptably firm. This seems to further demonstrate the effects of CLA are not simply due to changes in feed intake. The researchers say they will try to better quantify differences in belly firmness in future trials in an effort to better define this effect. The question of how CLA improves belly firmness remains to be answered. The fatty acid profiles of the bellies from this trial are currently being determined, and the results will appear in a future report.

Analysis of the fatty acid composition of loins is reported in Table 5. CLA-fed pigs deposited more CLA in their loins, and deposited an amount of CLA which is similar to what they were fed (0.6%). The loins of CLA-fed pigs contained more saturated fatty acids and less unsaturated fatty acids, which resulted in a higher saturates-to-unsaturates ratio. CLA-fed pigs tended to have less mono- and poly-unsaturated fatty acids, but the results were not significantly different. Thus, the feeding of a poly-unsaturated fatty acid resulted in an increase in the amount of saturated fats. This result differs from the researchers' previous experiences in which the feeding of unsaturates has decreased the saturate-to-unsaturate ratio and resulted in a decrease in fat firmness. CLA may be affecting the regulation of genes that determine fatty acid composition. Future trials will determine the effects of CLA on such genes.

Future trials need to determine the effects of CLA on growth, composition and quality, and also seek to further understand the underlying biology that controls such traits. Because the effects of CLA will likely vary across genotypes, learning how CLA affects growth and gene expression will enable researchers to better determine at what level and for what duration CLA should be used by producers.

Researchers: J.M Eggert, M.A. Belury, and A.P. Schinckel, Departments of Animal Sciences and Foods and Nutrition, Purdue University. Contact Schinckel at (765) 494-4808.

Accelerating Ovarian Maturation

Vaughan Lee and John McGlone, Texas Tech University researchers, have been conducting an ongoing study focusing on increasing the reproductive output of gilts and sows.

The study is assessing the efficacy of treating female pigs with a specific growth factor to accelerate ovarian maturation and increase the number of developing follicles or ovulations. According to McGlone, the growth factor known as porcine EGF, is produced naturally in the pig and has been identified in many species.

Treatment of pig ovaries with EGF in culture resulted in an increase in two biochemical indicators of follicular development. These results indicate EGF has the potential to directly stimulate ovarian maturation.

The first studies involving live pigs used 18 gilts between the ages of 2-4 weeks in either control or EGF treatment groups. The gilts underwent minor surgery for placement of subcutaneous osmotic pumps. The pumps delivered a specific dose of EGF or a control solution over a 14-day period. During this time, both groups were individually housed. General health, feeding and behavioral observations were made and recorded.

Organ weights and tissue samples were obtained from both control and treatment groups at 70 days of age. Laboratory testing and data analysis from the early studies have been encouraging, McGlone reports.

EGF in live gilts caused a 70% increase in the number of activated follicles at 2.5 months of age, with no apparent adverse effects on health.

"In future studies, gilts will grow to maturity, and will be examined to determine whether puberty is accelerated and ovulation rate is increased," McGlone says.

Large-scale field testing will be undertaken at later stages of the project. Further development of the delivery system will enable easier and more effici ent treatment of large numbers of gilts in the commercial setting.

"Several diagnostic and therapeutic procedures aid the industry in increasing swine reproduction," McGlone relates. "However, stimulating early puberty and increasing ovulation rate have not yet been achieved by using modern biotechnology tools."

Researchers: Vaughan Lee, Department of Cell Biology and Biochemistry, Texas Tech University Health Science Center, and John McGlone, Professor of Animal Science and Director of the Pork Industry Institute, Texas Tech University. Phone McGlone at (806) 742-2826.

Two Parasites Targeted in Certification Programs

Before long, the pork industry will have certification programs underway for two pork parasites, Trichinella spiralis and Toxoplasma gondii.

USDA's Agricultural Research Service (ARS), university scientists and the National Pork Producers Council are involved in cooperative research developing tools to implement and monitor certification systems on the farm.

Trichinella is a nematode worm found in muscle meat. Though incidence has been in decline for decades, its continued, high-profile existence has served to tarnish the image of the pork industry.

Toxoplasma is a single-celled protozoan parasite found in muscle and organ tissue. Its existence has only been documented in recent years. The role of pork in human toxoplasmosis is unknown.

Good news is that both parasites are disappearing. Modern swine husbandry has made it almost impossible to find hogs infected with trichinella. Even those that are detected are at very low levels and pose virtually no risk to public health.

Toxoplasma infection has also declined, but still occurs in 2% or more of market hogs and at higher rates in breeding stock.

In cleaning up the two parasites, producers must maintain stringent management programs coupled with testing.

Pigs can only become infected with trichinella by eating infected muscle tissue. Rats and wildlife are the most common sources of trichinella. Prevention consists of rodent control programs and barriers to wildlife.

Control of toxoplasma is a bit tougher. Pigs can become infected by eating infected tissues such as rodents and small mammals. But in addition, cats pass a resistant stage of toxoplasma (the oocyst) which if ingested can infect the pig. So while prevention includes rodent control, it largely depends on isolation of cat populations from pigs, feed and feed storage areas.

The trichinella control program is well underway. A farm audit has been developed which documents good production practices that limit the risk of infection. The audit could lead to producers selling their product as "trichinae certified." A similar audit is proposed for toxoplasma.

To support certification, it will be necessary to verify freedom from infection. ARS scientists have developed a simple blood test for both parasites which takes just minutes to perform using samples collected at slaughter. These same tests can be run using fluids collected from small meat samples.

Researcher: R. Gamble, Parasite Biology and Epidemiological Laboratory, Agricultural Research Service, Beltsville, MD. Phone ARS at (301) 504-8431.

Vitamins E and C May Improve Pork Quality

Canadian researchers found supplementing finishing hog diets with the anti-oxidant vitamins E and C resulted in color stability, reduced drip loss and reduced lipid oxidation in fresh and cooked pork. Researchers from the University of Guelph, Ontario, Canada, discovered gilts responded more positively in most variables tested than barrows did when fed supplemental vitamins.

Studies of vitamin E in market hog diets show a benefit in color, drip loss and lipid oxidation. Supplementation time and levels for many studies have been varied, and no concise recommendation has been developed, the researchers say. There also is no research on the additive effects of vitamin E and C supplementation on pork quality.

Vitamin C is a well-known, free radical scavenger, and has been shown to improve lipid stability in beef. Vitamin C also reduces the alpha-tocopheryl radical, thereby regenerating vitamin E.

Experiments were conducted to determine what effect the addition of vitamins E and C in the diets of market hogs have on the dressing percentage, color and drip-loss of fresh pork, and the lipid oxidation of fresh and cooked pork and cooking loss.

The studies were conducted at Ridgetown Swine Research Center. Three-hundred, commercial, crossbred market hogs were used to test the effects of different levels of vitamin E. The levels tested were control, 200 IU/kg. (90.91 IU/lb.) or 400 IU/kg. (181.82 IU/lb.) of feed supplementation level. The diets were fed for three weeks before slaughter, and treatments of 400 IU (181.82 IU/lb.) of vitamin E plus 500 mg. (227.27 mg./lb.) vitamin C per kg. of feed fed for either two or three weeks before slaughter.

Barrows and gilts were penned separately. All animals were slaughtered at approximately 231 lb. of body weight.

The loin was removed from one side of the carcass after a 24-hour chill. A 48-hour drip loss and color (Minolta Chroma-Meter) measurement were determined on duplicate cores of longissimus muscle. Fresh loin roasts were weighed, cooked and re-weighed and packaged under normal retail lighting conditions for analysis at 24 hours and 144 hours after cooking. Core samples of the roasts were taken fresh and at 24 hours and 144 hours after cooking to test for lipid stability.

Vitamin supplementation had no effect on the dressing percentage of the hogs. Drip loss was not significantly different across treatments. However, hogs fed for two weeks with vitamins E and C had 6.6% lower drip loss than control hogs. (10.5 +/- .35 versus 9.8 +/-.35% drip loss for control and vitamin E and C treated, respectively).

There was no effect of treatment on the color of barrow meat. The color of gilt meat was shifted further into the red range of the color spectrum with vitamin E and C treatment fed for two weeks. There was no effect of vitamin E fed alone at either level on the lipid oxidation of fresh or cooked pork. However, there was a significant effect of lowering lipid oxidation when vitamin C was added.

Treatment had no effect on cooking loss, however, gilts treated with vitamins E and C for both supplementation times had 2% lower cooking loss than barrows.

The researchers say pork quality is influenced by many variables and the repeatability of measurements is a concern. Split-sex feeding may be necessary to take advantage of the benefits of vitamin supplementation.

Vitamin C may well be an important partner with vitamin E in preserving cooked and/or processed pork. Future research will focus on optimizing the amount, delivery (feed or water) and supplementation time needed to create a cut of pork that provides an effective source of antioxidants in addition to a high quality, palatable source of protein.

Researchers: Vernon R. Osborne, Ridgetown College, Roger R. Hacker and E. Jim Squires, Department of Animal and Poultry Science, University of Guelph. Contact Hacker at (519) 824-4120.

Alternative to Sodium Selenite Found for Sows

A recent Ohio State University study compared the use of an enriched selenium yeast (1000 ppm) or sodium selenite added to sow diets when they entered the farrowing house, or approximately 5-6 days prior to farrowing.

Although the FDA has approved the use of selenium in the forms of sodium selenite or selante in swine diets up to a supplemental level of .3 ppm, deficiencies of vitamin E and selenium still occur in many of the nation's swine herds. This deficiency seems to be more common in parts of the U.S. where the grain content of selenium is low. However, deficiencies also occur in the progeny of older, higher-producing sows.

The characteristics of neonatal pigs affected by a selenium deficiency are weakness, lack of desire to nurse the sow, mulberry heart and the occurrence of iron toxicosis. The latter condition is noted when neonatal pigs go into shock and die when given a 100 to 200 mg. injection of iron to prevent anemia.

Perhaps the period when the selenium deficiency is most prevalent in young pigs is within a few weeks upon weaning, where the largest, fastest-growing pigs suddenly die with no outward symptom. A recent summary of milk selenium contents by Ohio State University (OSU) scientists has documented that the milk selenium content of sows declines as they mature, thus providing less selenium to the pig upon birth and at weaning.

The OSU research trial used a total of 45 sows. The sows were fed diets with either .15 or .30 ppm inorganic or organic selenium. In addition, a non-fortified diet (basal) and a diet with a combination of the selenite and organic yeast product were fed in a 50:50 blend. Each blend provided .15 ppm selenium for a total of .30 selenium in the sow's diet..

The results, presented in Figure 2, demonstrate that the sodium selenite resulted in a small increase in the milk selenium content of the sows, but the incorporation of the organic selenium from the yeast resulted in a dramatic increase in milk selenium content.

The combination of both selenium sources produced milk selenium results that were similar to those when the organic selenium source was fed. This suggests that the inorganic form of the mineral was not effectively transferred to the mammary tissue and thus the milk supply of the nursing pig.

Other data demonstrates the blood selenium content of the pigs' blood was higher when the organic selenium was fed to the sow, thus improving their status at the time of weaning. Although the use of organic selenium has not been approved for use by the FDA, its approval is expected by early 1999.

Researcher: Don Mahan, The Ohio State University, Columbus, OH. Phone Mahan at: (614) 292-6987.

Early Weaned Behavior May Last Lifetime

Pigs weaned early have been known to develop behavioral vices. This fact has produced restrictions on weaning age in several countries.

No one has known if this behavior extends into grow-finish and questions have been raised whether diets are contributing to continuation of these vices such as belly nosing.

Researchers at Prairie Swine Centre in Saskatchewan, Canada investigated the effects of early weaning on behavior through the nursery and grow-finish periods.

Two treatment groups were compared: weaning at 21 days or 12 days of age. Pigs were housed in separate, but identical, on-site nursery rooms and within the same, grow-finish rooms.

Result was that pigs weaned at 12 days of age were slower in developing normal eating patterns than their counterparts weaned at 21 days of age. But the younger weaned pigs developed more normal eating behavior by 48 hours after weaning (See Figure 1).

The eating patterns of the two groups are depicted in Figure 1. The 21-day-old weaned pigs gradually increased eating over each 12-hour period following weaning.

In contrast, pigs weaned at 12 days old did very little eating before 36 hours postweaning. For the next 5-6 weeks, those early weaned pigs spent more time eating and drinking, but also in nosing other pigs and chewing on objects. This behavior persisted into grow-finish.

The Canadian researchers argue the fact that the higher level of chewing and nosing persists into grow-finish proves the behavior developed in an early weaning environment may have a lasting impact on animal behavior. There was no impact of behavioral vices on productivity in the study.

Attempts at eliminating these behavior-related concerns have not proven successful. Steps have included addition of plasma protein in the diets.

Researchers: Harold W. Gonyou, Eduardo Beltranena, Lee Whittington and John F. Patience, Prairie Swine Centre, Saskatoon, Saskatchewan, Canada. Phone Gonyou at (306) 373-9922.

Development of An Odor-Rating Model

In the second year of the project at the University of Minnesota, limited research data suggests that air dispersion models are an accurate means of tracking odor emissions from livestock and poultry operations.

A team of agricultural engineers at the school compared odor emission data compiled by a computer model with a group of seven "nasal rangers" who subjectively collected data in the field.

Comparing data on odor one-on-one between the model and the human sniffers will reveal some differences. But overall, the preliminary results show the procedure used was rational and useful in predicting livestock and poultry odor dispersion, if proper field verification is carried out.

Although there are many models currently available for predicting livestock odor dispersion, few have gone through an extensive validation process using field measurements, point out the University of Minnesota researchers.

That makes this research to develop an odor-rating system of particular significance. It paves the way for the use of an air dispersion model in predicting the spread of livestock odor from farms.

In the first round of trials, moderate-sized farms studied had confinement facilities that are mechanically and naturally ventilated, plus animals in open feedlots. These operations feature a variety of manure handling and storage systems including earthen storage basins, deep bed/litter pack, above ground tanks and deep pits.

It was decided that the second trial should involve farms that have large odor sources. Among the farms added was a farm with 3,000 finishing hogs.

For further verification of the air dispersion model, the nasal rangers sampled additional hog farms that were similar to what the model measured, but different in size. Four finishing operations were specifically monitored. These farms have the same manure handling and storage systems (deep pits) and same size curtain-sided buildings. The only difference was that the number of barns varied from site to site.

In this way, the influence of farm size on odor dispersion can be measured for distance and quantity, and a better understanding of how the dispersion model works can be achieved.

For starters, for the model to be verified requires large quantities of field measurements. Seven trained sniffers conduct on-site odor plume measurements. They rank the intensity of odors they sniff based on a numerical scale of 0 (no odor) to 5 (intense odor). If a sniffer could not distinguish between two levels, they would record a half level. The odor sniffers are required to wear a protective charcoal mask at all times except for the times they are actually sniffing for odors.

In this study, measurements are taken every 10 seconds during a 10-minute period, for a total of 60 readings per individual. Distances between 83 ft. to 1,320 ft. (depending on site and strength of odor source) were marked off at the centerline of the downward odor plume. Sniffers were positioned at points perpendicular to this centerline from 17 ft. to 66 ft. apart (See Figure 2) to cover the plume width.

Before each sniff, the nasal rangers would calibrate their noses (sensory system) by sniffing a static scale of N-butanol supplied to the group. To avoid a reduction in the sensitivity of the sniffers, a medium-range odor concentration was used in the first measurement at a distance of 330 ft. A second measurement was taken at 660 ft. and a third one at 1,320 ft. Weather information was recorded by an on-site, portable weather station at a 10-second interval to match the frequency of downwind odor data collection by the nasal rangers.

To calculate the odor intensity experienced by each panelist, average odor readings were converted to an "odor unit" by which a comparison can be made between the output of an odor dispersion model, expressed in odor units, to the levels detected by the nasal rangers in the field.

Researchers: Larry D. Jacobson, Richard E. Nicolai, David R. Schmidt and Jun Zhu, University of Minnesota, St. Paul, MN. Phone Jacobson at (612) 625-8288.

Breeding for Better Disease Resistance

It has been known for some time that not all pigs are susceptible to infection with K88 E. coli bacteria.

Recently, South Dakota State University (SDSU) researchers have determined how that resistance occurs and have estimated the number of pigs that possess the resistance trait.

The SDSU researchers identified a glycoprotein (protein containing sugar molecules) called IMTGP that is produced in the intestinal lining of some, but not all pigs.

Because K88 E. coli attach to IMTGP, it appears that this glycoprotein allows the bacteria to adhere to intestinal cells and grow there.

Germ-free pigs that had intestinal cells with IMTGP were found to be highly susceptible to K88 E. coli. Pigs that did not have IMTGP in their intestines were resistant to the E. coli bacteria.

Also, the intestines of pigs tha t produced IMTGP were highly colonized with K88 E. coli. But the intestines of pigs that did not produce IMTGP were not.

"This discovery suggests that selective breeding for disease resistance will be feasible once practical tests for detection of IMTGP are developed, or the genes responsible for its production are developed," says David Francis, SDSU lead researcher in the project.

Despite lack of a practical test to identify pigs that produce IMTGP, there is a way to identify pigs resistant K88 E. coli. The bacteria is able to adhere to intestinal cells isolated from some pigs, but not others.

All pigs that produce IMTGP are among those that allow the E. coli bacteria to adhere to intestinal cells. Thus, no IMTGP-producing animals are among the pigs that don't allow this adherence. Pigs that don't allow adherence are therefore resistant to the bacteria.

To prove resistance occurs, SDSU investigators tested intestinal cells from 96 weaned pigs from 24 purebred farms. There was some breed to breed variation, but 49% of the cell specimens from pigs of the Chester White, Duroc, Hampshire and Yorkshire breeds failed to support adherence of the K88 E. coli. This suggests that half or more of the pigs in the sample, and perhaps swine population, are disease resistant.

Identification of resistant animals, and breeding for the resistant trait, may become practical in the future. Also, with greater understanding of how IMTGP promotes bacterial colonization, it may be possible to develop a specific, non-antibiotic therapy to block the attachment of K88 E. coli to intestinal cells of susceptible piglets.

Researchers: David Francis, Alan Erickson, Philippe Grange and Diane Baker, South Dakota State University, Brookings, SD. Phone Francis at (605) 688-5680.

Improving Rebreeding Performance of Early Weaned Sows

Researchers at the University of Guelph, Ontario, Canada, suggest a successful early weaning program can improve sow productivity by increasing the number of litters per sow per year.

An experiment was conducted to evaluate the effects of early weaning on the subsequent reproductive performance of first parity sows. Roger Hacker, University of Guelph animal scientist, says early weaning (at less than 14 days old) of litters often results in reproductive problems in sows. Problems can range from irregular heat cycles, an increase in weaning-to-estrous interval, reduced conception rates, development of cystic ovaries and small, subsequent litter sizes.

Conflicting results are present in existing literature on the topic of early weaning. The uterus has not completely recovered (involuted) until day 17 to 20 after farrowing in sows nursing litters, and the sow usually ovulates more eggs than the uterus can accommodate. Vernon Osborne, University of Guelph animal scientist, says high serum cortisol levels, which can indicate stress situations, have been positively correlated to reduced sow fertility. All these variables result in early embryonic loss and lost profitability.

This experiment was designed to determine the effects of weaning sows at day 7 and day 14 vs. day 28 post partum on the degree of stress (cortisol), ovarian function (cystic ovaries, ovulations), farrowing to fertile estrous interval, and subsequent litter size of first parity sows.

Eighteen first parity, purebred Yorkshire sows were randomly assigned to an experimental group. The sows were weaned at 7, 14 or 28 days of lactation.

Sows received the same diet and management practices throughout the trial period. Blood samples were collected for plasma cortisol analysis in the morning and afternoon on specified days during lactation and around weaning.

Sows were moved to a group pen after weaning and were mated naturally on the first day of standing estrous. Sows were sacrificed at approximately 50 days into gestation. The entire reproductive tract was excised for autopsy analysis. Reproductive tract analysis included counting the number of viable and poor fetuses, number of corpus luteum, mean diameter of corpus luteum and the incidence of ovarian cysts.

Table 1 shows the variables collected. Four sows on the 14-day weaning period were culled due to various reasons, resulting in missing information. The statistical analysis was adjusted for the missing data.

There was no effect of pigs weaned from the initial litter on the subsequent reproductive performance of all sows. The number of days from weaning to estrus was not significantly different across weaning times.

The ratio of ovulations (number of corpus luteum) to viable fetuses (percent of embryo to corpus luteum) was not significant across weaning times, but there was a substantial range in all weaning times (Table 1). Serum cortisol levels were not different and stress did not appear to be a factor in reproductive performance.

Optimum reproductive success includes ovulation, fertilization and implantation. Osborne says early weaning does not appear to affect ovulation. The reasons for embryo losses in early gestation are still not well understood. A lower number of embryos may be a consequence of incomplete uterine involution and not of early weaning. "The data in Table 1 illustrates that the reproductive response is unique for each sow and controlling the variance among animals is an ongoing challenge in the industry," Hacker says.

Researchers: Vernon R. Osborne, Robert M. Liptrap, and Roger R. Hacker, University of Guelph. Phone Roger Hacker at (519) 824-4120.